The Turkish army blamed the Syrian regime for an air strike on Thursday in northern Syria that killed three soldiers and wounded 10, it said in a statement.
"In the air strike assessed to have been by Syrian regime forces, three of our heroic soldiers were killed and 10 soldiers wounded, one seriously," said the statement on its website.
The army said the strike took place at 3:30 am (0030 GMT). Turkish media reported earlier that the attack in the Al Bab region was by Islamic State (IS) jihadists.
This is the first time the army has blamed President Bashar al-Assad's regime for an attack killing Turkish soldiers during Ankara's three month operation in northern Syria.
The Turkish military launched the operation -- dubbed "Euphrates Shield" -- in August supporting Syrian opposition fighters seeking to retake territory from IS in northern Syria with tanks and aerial support.
Hundreds of Turkish soldiers are taking part in the operation, which President Recep Tayyip Erdogan said this week was pushing forward with its aim of taking Al Bab from IS.
"We reached Al Bab right now and besieged it from the west," the president said in a speech on Tuesday.
The latest deaths raise to at least 15 the number of Turkish soldiers killed since Turkey began its operation in northern Syria.
Most were killed by IS but one soldier was killed in an attack blamed on the Kurdish People's Protection Forces (YPG).